The present invention concerns a process for the production of a circuit carrier fitted with at least one surface-mount LED (SMD-LED), having the features described below, and a circuit carrier having the features described below.
To implement light-optical applications based on surface-mount LED components (SMD-LED), highly precise mounting of the SMD-LED components on a circuit carrier is required. Examples are front headlights, daytime running lights, flashing indicators, active bending lights on motor vehicles, the light sources of which are LEDs.
In that respect the SMD-LEDs are to be mounted in position in relation to one or more defined reference points on the circuit carrier, then an optical system (for example attachment lenses) can be oriented in relation to those reference points.
Hitherto SMD-LED components have been placed on the circuit carriers using the so-called “Pick & Place” process and then soldered in the “Reflow” process. In that case the final position of the light-emitting region of the LED is determined by the following factors:                the tolerances in the LED component (for example the position of the light-emitting region relative to the outside contour of the LED or relative to the position of the LED terminal pad),        the tolerances in the circuit carrier which determine the position of the soldering pad (for example position of the conductor track relative to the contour of the circuit carrier and/or a through hole, position of the solder mask relative to a conductor track position), and        the movement of the SMD-LED in the Reflow soldering process, caused by “slumping” of the solder paste in the pre-heating zone and the wetting forces of the solder upon melting in the peak zone (floating lift).        
The final levels of positioning accuracy which can be achieved with that process in respect of the light-emitting region of SMD-LED components are already more than +/−110 μm solely when considering the tolerances of the SMD-LED and the circuit carrier (still without taking account of the action of the Reflow soldering process).
The effects of the Reflow soldering process produce additional positioning inaccuracies, in particular in the area of angular and tilting positional truth in respect of the SMD-LED components.
Mounting of the SMD-LED by means of current silver sintering processes is out of the question as those processes are linked to unacceptably long processing times of more than 10 seconds.